The Children's Hospital of Philadelphia
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Hypoplastic Left Heart Syndrome — How HLHS Develops

J. William Gaynor, MD: Hypoplastic left heart syndrome, which some people call HLHS, is one of the more common forms of congenital heart defects.

Peggy McCann, RDCS: There's a couple things that make up the HLHS variant, and the number one is usually small left ventricle and associated with it all small left-sided structures, by that I mean a small mitral valve, a small aortic valve, a small left ventricle and a small aortic arch.

J. William Gaynor, MD: There's almost infinite variety in the actual clinical findings.

Peggy McCann, RDCS: And typically, during the initial scan things will be apparent on the ultrasound right away.

Zhiyun Tian, MD: So each piece of information are very important. We actually can help the physician provide information to the family.

Thomas Spray, MD: Basically, hypoplastic left heart syndrome is a situation where there is an underdeveloped left ventricle.

Peter Gruber, MD: That's usually the pumping chamber that pumps blood from the heart to the rest of the body.

Thomas Spray, MD: It can involve the mitral valve, which is the valve entering the left ventricle. It can involve the left ventricle itself. And it can involve the aorta, which is the artery leaving the left side of the heart to the body.

J. William Gaynor, MD: The aorta, which carries blood to the body, is frequently very small and blocked.

Thomas Spray, MD: The ultimate problem here is that the left ventricle cannot support the circulation.

Peter Gruber, MD: So without a left side that's big enough, it's not strong enough to provide blood flow to the body.

J. William Gaynor, MD: It's a very severe form of heart disease, and if not treated medically and then surgically early after birth, almost every infant will die within the first few weeks of life.